Cantilever type stool



Aug. 19, 1953 E. w. M KNlGHT 2,848,037 H GAN'I'ILEVER TYPE srooL 2 Sheets-Sheet 1 Filed Aug. 16, 1954 IN VEN TOR.

EDGAR W- MUG/(NIGHT BY A TTOR/VEYJ Aug. 19, 1958 E. w. M KNlGl-IT 2,848,037

CANTILEVER TYPE STOOL Filed Aug. 16, 1954 2 Sheets-Sheet 2 0 mm ,m MM M N fi M r w. m m m United States Patent CANTILEVER TYPE STOOL Edgar W. MacKnight, San Leandro, Calif., assignor, by decreeof distribution, to Bonna MacKnight Application August 1-6, 1954, Serial No. 451,805

a 4- Claims. (Cl. 155-81) My invention relates to a cantilever type stool and more particularly to one adapted for use by dentists, etc., when working on patients.

Among the objects of my invention are (1) To provide a novel and improved stool of the cantilever type;

(2) To provide a novel and improved stool of the cantilever type for use with dental chairs or the like;

(3) To provide a novel and improved stool of the cantilever type which can be firmly anchored to a dental chair or the like and in such manner as toprevent creepingof the one with respect to the other;

(4) To provide a novel and improved stool of the cantilever type which can be pivotally anchored with respect to the base of a dental chair or the like and in which the resistance to swingcan be adjusted;

(5) To provide a novel and improved stool of the cantilever type incorporating a slightly tilted seat capable of limited linear movement radially of its point of anchorage but which is normally urged to the remote point of such limited movement;

(6) To provide a novel and improved stool of the cantilever type capable of fulfilling the foregoing objects, yet which structurally is simple and rugged.

Additional objects of my invention will be broughtout in the following description of a preferred embodiment of the same taken in conjunction with the accompanying drawings, wherein Figure 1 is a three dimensional view, partly fragmentary, depicting the general overall appearance of the stool of the present invention;

Figure 2 is an enlarged view in section of the radial arm and associated structural portions of the stool of Figure l;

Figure 3 is a viewin section taken in the plane 3--3 of Figure 2; I

Figure 4 is a fragmentary view in plan of the anchoring portion of the stoolbase;

Figure 5 is a view depicting the details of the means for coupling portions of the stool base;

Figure6 is a view depicting the details of clamping means incorporatedin the stool base;

Figure 7 is a view in section of a seat assembly which is particularly suitable for incorporation in the stool of the present invention;

Figure 8 is a view in .section taken in the plane '8-.-8 of Figure 7;

Figure 9 is a view in section taken in .the plane 9-9 of Figure 8.

Referring to the drawings for details ofmy invention in its preferred form, the same involves a base 1 adjacent one edge of which, there is rigidly mounted a pivot post 3. Surrounding the pivot post and spaced by a sleeve 5, are a pair of bearings 7, 9 on which to rotatably mount a hub 11 from which extends a radial arm 13, preferably at a slightly upwardly directed angle with respectrto the horizontal. The radial arm at its free end terminates in a collar 15 within which is fixed the outer 2,848,037 *Ratente'd Aug. '19, 1958 tubular member 17 of a telescopically adjustable standard or post 19, along the inner surface of which is aflixed a longitudinal rib or key 21.

The inner telescopic member is a tubular member 23 carrying at its lower end a circular slide bearing 25 having a notch provided therein to mesh with the key to preclude rotation of the inner member with respect to the outer member, while permitting telescopic movement between the two. At its upper end, the inner member slidably passes through a fixed bearing '27 mounted within the upper end of the outer member.

The inner telescopic member carries a seat assembly 29, which preferably is of the type forming the subject matter of my application for seat assembly, Serial No. 373,349, filed August 10, 1953. Such assembly involves a seat 31 and its associated mechanism 33.

The associated mechanism includes a rod or spindle 35 journalled within the inner telescoping member and extending beyond the upper end thereof. At this end, there is fixedly mounted an arm 37 which terminates at its other end in a bearing 39, in which is journalled a short shaft 41 which protrudes from the bearing at either end thereof.

At its upper end, this short shaft has aflixed thereto a seat arm 43 in the free end of which is journalled the stem 45 of a suitable seat 31, spaced bearings :49, 51 being preferably provided for this purpose.

As thus far described, the path of movement of the seat with respect to the axis of the supporting telescopic member, is indeterminable and not fixed. This is so because, under the circumstances, the seat is adapted to swing indiscriminately about the short shaft as an axis, while at the same time, the short shaft is adapted to swing indiscriminately about the axis .of the supporting telescopic member. Therefore, in order to pre-establish the permissible path of movement of the seat with respect to the axis of the supporting member, both of the aforementioned swinging movements must be controlled with respect to each other.

This is accomplished by fixedly mounting on the upper end of the inner telescopic member, a sun gear 53, while at the lower end of the short shaft 41, I provide a plane- 'tary gear 55, and then connect the two gears by some drive means such as a chain drive 57.

With such a connection, any swinging movement on the part of the short shaft in an are about the axis .of the inner telescopic member which supports the same, will cause the seat to swing inan arc in opposite direction about the short shaft axis. By selecting a proper relationship between the ratio of arm lengths and the gear ratio, substantially linear movement of the seat may be realized and along a path through the axis of the supporting member. A gear ratio of 2 to 1 between the sun gear and planetary gear will satisfy the requirements, where both arms are of the same length.

To assure that such linear movement shall be confined to a particular direction, namely in a plane through the axis of the radial arm, which will then provide for linear movement toward and away from a patient, the seat and its associated mechanism should be initially assembled so that a line joining the axis .of the supporting telescopic member and the center of the seat, shall sight along the axis of the radial arm, and to assure maintenance of such directional adjustment, the sun gear must be fixed against rotation on its axis. This is accomplished by the previously described key interlock between the inner and outer telescoping members of the standard.

Extending upwardly from the sun gear, are a pair of stop pins 59, 61 disposed on a line preferably slightly off center. Such stop pins stand in the path of movement of the arm 37 and thus preclude the short shaft from I 6| ever reaching a dead center position, which might interfere with smooth, effortless movement of the seat. Ease of movement of the seat between its forward and its protracted position will, therefore, always be assured.

A shroud 63 may be installed over the planetary gear arrangement and when so installed, is held out of contact with the chain drive by a bolt 65 extending through the arm 37.

In the absence of an overpowering force, the seat is urged to its retracted or outermost position and restrained against movement therefrom. This is accomplished by means involving a flat coil spring 67 encircling the sun gear and having one end anchored in said gear and its other end hooked around the lower end of the bolt 65 which is the same as being anchored to the arm 37. The spring is preferably disposed in a circumferential groove formed in the gear by anchoring one end of a length of spring wire in a recess in a wall of such groove, wrapping such wire around the gear and then hooking its free end about the bolt 65.

Any force suflicient to overcome the resistance offered by the spring, would cause the seat to move forward in the direction of a patients chair, the spring in the meantime being wound tighter to build up an increased restoring force, so that upon removal of said overcoming force, the seat will be restored to its retracted position.

Under these conditions, the entire seat assembly may be adjusted to a slight tilt angle with the vertical, say of the order of 2 to degrees without the seat shifting from its retracted position. This I prefer to accomplish by aflixing the standard to the end of the radial arm at a slight tilt angle in the direction of the pivot post axis and of the order indicated.

One of the advantages derived from this relationship resides in the fact that the weight of the operator on the seat will provide a component force in the forward direction of its movement, thus facilitating the use of the seat assembly in carrying the operator toward the patient. Working from a seat so tilted, places the operator in a more comfortable and relaxed posture, at the same time avoiding the necessity of consciously holding the seat against the retraction by the spring, thus enabling the operator to work more effectively and effi ciently.

At the upper end of the outer telescopic member, there is provided means 69 for locking the inner telescopic member 23 in a vertically adjusted position. Such means comprises a rectangular housing of two sections, namely a lower section 71 which is integrally united to the upper end of the outer telescopic member 17, and an upper section 73 which provides a matching fit with the lower section. The upper section is held to the lower section by a bolt 75, both sections having vertically aligned openings to permit passage of the inner telescopic member.

Within the rectangular housing is a locking plate 77 which has a central beveled opening therethrough, through which the inner telescopic member may comfortably pass when such locking plate is in a horizontal position.

At one end, this locking plate is loosely supported between a shoulder 79 and a flange 81 formed by suitably crimping a piece of sheet metal and welding the same into the lower section of the housing, while at its opposite end, the plate is provided with a perforation through which the bolt 75 passes, the plate being normally urged downwardly at this end, against the inner telescopic member by a compression spring 83 thereabove.

Disposed below the locking plate in line with the compression spring 83 is a lip 85 constituting one end of a lever 87, preferably in the form of a stiff wire loop which extends through a wall of the housing and fulcrums on the edge of the opening through which it passes. Under the action of the compression spring, the tube will, in the absence of any opposing force remain in its pre- 4 vailing adjustment, and any weight or pressure applied to the upper end of the inner telescopic member, as when one sits upon a seat carried thereby, will only serve to enhance the binding effect of the locking plate thereon.

When it is desired to adjust or change the elevational position of the seat which is carried on the inner telescopic member, a downward pressure on the exposed end of the lever will lift the lower end of the locking plate, thereby bringing the locking plate to a horizontal plane, whereby the inner telescopic member will be freed for movement along its vertical axis.

A limited amount of adjustment is provided for in the radial arm, to permit adjustment of the radial distance of the seat from the patients chair, and this is accomplished by making the radial arm of telescoping parts 89, 91 with a pair of bolt holes 93, 95 in the outer member and a plurality of similarly spaced bolt holes 97, 99 etc. in the inner member, and bolting the two members after adjusting the inner member to bring a selected pair of its openings into alignment with the bolt openings in the outer member.

To provide adequate anchorage for the stool and prevent creeping thereof relative to the patients chair, the base 1 is of ring shape adapted to encircle and be locked to the flange 101 of the base of the patients chair, whereby the full weight of the patients chair and any occupant thereof will serve to anchor the base of the stool and support the dentist or other operator thereon.

Such ring base includes a pivot post anchor portion including a crescent shaped channel section 103 having an arcuate inner edge to receive the flange of the base of a patients chair. Backing this channel section and welded thereto along the mid-section thereof, is a substantially rectangular floor plate 105. Welded to the upper surface of this crescent channel section and overhanging this substantially rectangular plate, is a supporting strip 107 for the pivot post. The space between this supporting strip and the floor plate, immediately below the pivot post, is occupied by a spacer block 109 leaving suflicient room for the reception of the edge of a floor mat 111 such as that commonly employed by a dentist over the floor area normally occupied by him in his work.

The pivot post is of cylindrical form having a bore therethrough, the post being counterbored for the reception of a bolt 113 which extends through the supporting strip and spacer block and threadedly engages the floor plate to securely anchorthe pivot post.

A screw 115 through the inner edge of the supporting strip, is adapted to engage the flange of the base of the patients chair with suificient grip to securely position the flange in the arcuate channel section of this portion of the base.

An additional pair of base portions 117, 119, are required to complete the encirclement of the base flange of the patients chair in the preferred embodiment of the invention. Each is of arcuate channel construction, adapted at one end to match the channel section of the anchor portion to which it is removably coupled.

The means for coupling each such portion of the ring base to the pivot post anchor portion involves a tongue 121 affixed to an end of one of said portions along the outer surface thereof and terminating beyond said end in an inwardly directed tongue offset adapted to enter an oversized opening 123 in the proximate end of the anchor portion. A block 125 afiixed to such tongue adjacent the offest and of a size to substantially fill the remainder of such over-sized opening, serves to hold the tongue in its interlocking position when once assembled in the opening of the adjacent base portion.

Following such coupling of the ring base portions, such portions may be drawn tightly about the flanged edge of such patients chair by means involving a bolt lug 12 7 on the proximate free ends of the two adjacent ring base portions and a tightening bolt through such lugs. The stool may thus "be securely anchored to the patients chair, with no likelihoodof there being any creepage of one with respect to the other.

The weight of the patients chair resting on :the ring base of thestool, multiplied by its efiective moment arm, which @may be represented by thedistanceirom the center of the ring base to the outer edge of the floor plate, is more than adequate to counter balance the weight of the dentist or other operator when seated upon the stool. The stresses and strains set up in the ring base by this situation are gradually distributed by reason of the crescent shape of the pivot post anchor portion, thus avoiding any concentration of stresses which might cause fracture or bending of any of the component portions of the ring base of the stool.

In a stool of the type under consideration, free swing of the radial arm and seat assembly about the pivot post is undesirable from the viewpoint of possible injury befalling the dentist, should he unconsciously lean against the seat for support. A feature of the present invention lies in the means to forestall such an occurrence by introducing resistance to free swinging of the arm and seat assembly about the pivot post, and this objective I accomplish in a very simple and expeditious manner by merely introducing an adjustable set screw 129 through the hub in line for engagement with one of the hub bearings, whereby upon tightening of such set screw, the bearing and pivot post will be distorted from its true circular cross section, to introduce pressure against the hub at right angles to the axis of the set screw. It is apparent that such pressure may be altered to suit the desires of the individual and may be varied within wide limits.

From the foregoing description of my invention in its preferred form, it will be apparent that the same fulfills all the objects attributed thereto and while I have illustrated and described my invention in its preferred form, the same is subject to alteration and modification without departing from the underlying principles involved, and I accordingly do not desire to be limited in my protection to such details as I have illustrated and described, except as may be necessitated by the appended claims.

I claim:

1. A cantilever type stool comprising a ring base; a pivot post rigidly mounted on said base; a radial arm rotatably mounted on said pivot post; a standard mounted at the free end of said radial arm and carried entirely thereby; a seat assembly mounted on said standard; said base including a pivot post anchor portion having a channel section with an inner arcuate edge to receive the flanged edge of the base of a patients chair, additional base portions of arcuate form, sufficient to complete a circle, each such portion being of matching channel section to substantially completely enclose and contain the flanged edge of such chair base, means for removably coupling one portion of said ring base to another portion, said means involving a tongue affixed to an end of one of said portions along the outer surface thereof and terminating beyond said end in an inwardly directed tongue offset entering an oversize opening in the proximate end of the adjacent base portion to be coupled, and a block aflixed to said tongue adjacent said offset and of a size to substantially fit the remainder of said oversize opening, and means for drawing said ring base tightly about the flanged edge of such patients chair following assembly of said ring base thereto, said means involving a bolt lug on the proximate ends of two adjacent ring base portions, and a tightening bolt interconnecting said lugs.

' 2. A cantilever type stool comprising a ring base; a pivot post rigidly mounted'on said base; bearings surrounding said pivot post; a 'hub about said bearings; a radial arm extending from said hub; a standard mounted at the free end of said radial arm at --a slight tilt in the direction of said hub and carried entirely by said radial arm; a seat assembly mounted on said standard, said assembly including a seat, said base including a pivot post anchor portion having a channel section with an inner arcuate edge to receive the flanged edge of the base of a patients chair, additional base portions of arcuate form, sufficient to complete a circle, each such portion being of matching channel section to substantially completely enclose and contain the flanged edge of such chair base, means for removably coupling one portion of said ring base to another portion, saidmeans involving a tongue affixed to an end of one of said portions along the outer surface thereof and terminating beyond said end in an inwardly directed tongue offset entering an oversize opening in the proximate end of the adjacent base portion to be coupled, and a block aflixed to said tongue adjacent said ofiset and of a size to substantially fit the remainder of said oversize opening, and means for drawing said ring base tightly about the flanged edge of such patients chair following assembly of said ring base thereto, said means involving a bolt lug on the proximate ends of two adjacent ring base portions, and a tightening bolt through said lugs.

3. A cantilever type stool comprising a ring base; a pivot post rigidly mounted on said base; bearings surrounding said pivot post; a hub about said bearings; a radial arm extending from said hub at an upwardly directed angle; a standard mounted at the free end of said radial arm at a slight tilt in the direction of said hub and carried entirely by said radial arm; a seat assembly mounted on said standard, said assembly including a seat, said base including a pivot post anchor portion having a crescent shaped channel section with an inner arcuate edge to receive the flanged edge of the base of a patients chair, additional base portions of arcuate form, suflicient to complete a circle, each such portion being of matching channel section to substantially completely enclose and contain the flanged edge of such chair base, means for removably coupling one portion of said ring base to another portion, said means involving a tongue affixed to an end of one of said portions alongthe outer surface thereof and terminating beyond said end in an inwardly directed tongue offset entering an oversize opening in the proximate end of the adjacent base portion to be coupled, and a block affixed to said tongue adjacent said offset and of a size to substantially fit the remainder of said over-size opening, means for drawing said ring base tightly about the flanged edge of such patients chair following assembly of said ring base thereto, said means involving a bolt lug on the proximate ends of two adjacent ring base portions, and a tightening bolt through said lugs; and means for adjustably resisting free swing of said radial arm and seat assembly on said pivot post, said means involving a set screw in said hub and engaging one of said hub bearings.

4. A cantilever type stool comprising a ring base, a pivot post rigidly mounted on said base, a radial arm rotatably affixed to said pivot post, movable seat support- 1 ing means mounted at the free end of said radial arm and carried entirely by said radial arm, and a seat assembly on said supporting means, said base including a pivot post anchor portion having a channel section with an inner arcuate edge to receive the flanged edge of the base of a patients chair, additional base portions of arcuate form sufiicient to complete the circle, each such portion being of matching channel section to substantially completely References Cited in the file of this patent UNITED STATES PATENTS Hill Aug. 26, 1890 Donohoe Dec. 12, 1950 MacKnight Sept. 1, 1953 Mohr May 11, 1954 Murray Nov. 16, 1954 

